1. Field of the Invention
The present invention relates to the field of digital-to-analog and analog-to-digital converters. The present invention more specifically relates to so-called "delta-sigma" converters which perform a coding/decoding of the digital signals at a much higher frequency than the sampling frequency, and which use actual digital-to-analog and analog-to-digital converters on a single bit.
The present invention more specifically relates to exchanges of information, other than the data processed by the converters, between circuits communicating via delta-sigma converters.
2. Discussion of the Related Art
Delta-sigma converters are used, for example, in modems that transmit data over a telephone line. In such an application, an analog part of the circuit connected to the telephone line must be galvanically isolated from digital inputs/outputs of the modem connected, for example, to a digital signal processor or to a microcomputer. Signals other than the actual data must generally transit through the galvanic isolation barrier of the modem. These additional signals require additional isolation means, separated from the isolation means through which the data transit, which is prejudicial to the cost and bulk of the modem.
Delta-sigma converters are also used in other applications, for example, between a digital circuit for processing audio data and an analog circuit that restores or records an audio signal. In such applications, it is frequent that information other than the actual audio data have to be transferred between the digital and analog parts of the system. The transfer of such additional information conventionally requires additional links dedicated to this information.